Burkholderia pseudomallei: in vitro susceptibility to some new and old antimicrobials

The treatment of melioidosis currently involves the use of antimicrobials such as ceftazidime, trimethoprim-sulfamethoxazole, amoxicillin-clavulanate and doxycycline. Evaluation of other antimicrobials with activity against the organism continues to be pursued, however, as the causative organism, B. pseudomallei, may not always be susceptible to the above antimicrobials. This study aimed to test the susceptibility of Malaysian isolates of B. pseudomallei against imipenem, meropenem, ertapenem, moxifloxacin and azithromycin. 80 previously stocked clinical isolates collected between 1978 and 2003 from the UMMC, Kuala Lumpur were tested for in vitro susceptibility to these antimicrobials using the E-test minimum inhibitory concentration method. 100% of isolates were sensitive to imipenem and meropenem, 97.5% were sensitive to trimethoprim-sulfamethozaxole, 37.5% to moxifloxacin, and only a minority was sensitive to ertapenem (7.5%). Using breakpoints for Staphylococcus and Haemophilus, 5.0%-6.3% of isolates were sensitive to azithromycin. In conclusion, our findings support the in vitro efficacy of imipenem, meropenem and trimethoprim-sulfamethoxazole against B. pseudomallei. Moxifloxacin, ertapenem and azithromycin cannot be recommended for the treatment of melioidosis; however, further studies are needed to test the efficacy of azithromycin in combination with quinolones.